a(n) = (2*n+1)*(7*n+1).

Terms

a(0) =1a(1) =24a(2) =75a(3) =154a(4) =261a(5) =396a(6) =559a(7) =750a(8) =969a(9) =1216a(10) =1491a(11) =1794a(12) =2125a(13) =2484a(14) =2871a(15) =3286a(16) =3729a(17) =4200a(18) =4699a(19) =5226a(20) =5781a(21) =6364a(22) =6975a(23) =7614a(24) =8281a(25) =8976a(26) =9699a(27) =10450a(28) =11229a(29) =12036